Field of the Invention
The invention relates to an electroactive elastomer converter that comprises at least one electroactive elastomer layer having a top side and underside, and also an electrically conductive electrode body two-dimensionally connected to the top side at least in regions and an electrically conductive electrode body two-dimensionally connected to the underside at least in regions, wherein at least one electrode body in each case has an electrode surface facing the elastomer layer, and in which at least one opening is present to which a region in which there is no bond between the elastomer layer and the electrode body can be assigned.
Description of the Prior Art
Electroactive elastomer converters provide at least two electrode bodies that are arranged at a distance from each other and are usually of layered construction, between which a layer of dielectric elastomer is inserted, which has exceptional elongation properties, typically of over 300%. Elastomer converters of such kind are very often constructed in the form of a multilayer stacked structure of a plurality of elastomer and electrode layers in an alternating layer sequence. The stacked structure thus contains the elastomer layers of dielectric elastomer material, each in a two-dimensional bond between two electrode layers and which elastomer layers form a capacitive stacked structure. The application of a suitably selected electrical voltage to the electrode layers creates attractive electrostatic forces between the electrode layers, which in turn cause the elastomer layers to be compressed, particularly in the thickness direction. Due to the stacked construction of the converters, the changes in thickness of all of the elastomer layers present in the multilayer stacked structure are added together until they represent a change in the travel path that is useful for actuation purposes. On the other hand, a mechanical deformation of such a multilayer stacked structure in the thickness direction of the individual elastomer layers results in a change in capacitance of the capacitive stacked structure, which is useful for electrical energy generation or an electrical signal pick-up.
Elastomer converters of such kind that function according to the “Maxwell voltage effect” use non-compressible elastomers, which change shape according to their design and elongation properties but retain their tare volume when exposed to compressive forces. In order to match the lateral by orientated lengthwise extending capabilities of elastomer layers within a multilayer stacked structure, the electrode layers, which are each in a two-dimensionally bonded structure with the elastomer layers, have lateral expansion properties.
WO 2007 029275 A1 describes an electroactive polymer based actuator with a stacked structure and having an electroactive polymer in a strip having strip surfaces respectively contacted by a two-dimensionally elastic flat electrode to form a strip-like layer structure that is folded in serpentine form to provide a plurality of layered structure plies arranged one on top of the other in a stack. When an electrical voltage is applied to the flat electrodes, the compressive forces in the direction of the layer thickness act on the individual electroactive polymer layer plies so that the actuator is able to contract in controlled manner in the direction of the layer thickness.
The use of expandable electrode layers for constructing stacked elastomer multilayer converters using synthetic dielectric elastomer layers emerges from an article by Chuc, Nguyen Huu; Park, Jong Kil; Thuy, Doan Vu; Kim, Hyon Seok; Koo, Ja Choon; Lee, Youngkwan et al. (2007): Multi-stacked Artificial Muscle Actuator Based on Synthetic Elastomer. In: Proceedings of the 2007 IEEE/RSJ International, pages 771-776. In particular, the article describes elastomer converter systems with annular or rectangular elastomer and electrode layers.
U.S. Published Application 2007/0114885 A1 describes an elastomer multilayer stacked actuator having thin metal electrode layers. While the electrode layers are not stretchable due to the material they are made from, their corrugated structure enables them to undergo deformation along a preferred spatial axis.
U.S. Pat. No. 6,543,110 B1 discloses an elastomer multilayer stacked actuator, as illustrated in FIG. 2G, which provides multiple elastomer layers arranged on top of each other in a stack. Each layer is connected by an adhesive layer incorporating a spatially discontinuous electrode layer for activating the elastomer layers. In this way, the elastomer layers are bounded directly either by the adhesive layer or by the electrode surfaces.
The article by G. Kovac, L. During, S. Michel, G. Terrasi, “Stacked Dielectric Elastomer Actuaro for Tensile Force Transmisson”, Sensor and Actuators A 155 (2009), pages 299-307, contains a representative overview of the related art in terms of elastomer stack converters, all of which provide for the use of elastic electrode layers.
By virtue of the two-dimensionally elastic properties of both their elastomer and electrode layers, the known electroactive elastomer converter systems allow relatively large travel paths or changes in layer thickness. However, the dynamic response or operating characteristics of elastomer converters of this kind is limited to the individual layers by their two-dimensionally elastic properties both in the lengthwise elongation and in the direction of thickness. This applies particularly to the frequency range with which it is possible to recover electrical energy or electrical useful signals from mechanical movements, particularly vibrations, using known elastomer converters.